The present invention relates to a method for making slender seamless steel mold, and more particularly to a method for making seamless steel mold for manufacturing a grip sleeve of a golf club.
It is known that a general solid plastic conic article or cylindrical article is molded by an upper mold and an opposite lower mold detachably associated therewith. When a hollow conic article or cylindrical article is molded, an additional pin member must be disposed through the cavity defined by the upper and lower molds as shown in FIG. 8A. A sleeve member H having a through hole h as shown in FIG. 8B is molded in such a manner that a pin member P is disposed in a cavity R between the upper and lower molds M1, M2 of FIG. 8A to define an annular space. The plastic material is injected into the cavity from an injection gate S to form the sleeve H as shown in FIG. 8B. The thickness of the sleeve H is determined by the diameter of the pin member P. However, in general, the length of the pin member is much larger than the diameter thereof so that when suffering the strong injection force during the material injection process, the pin member P tends to deform into a curved configuration shown by the phantom lines in FIG. 8A. Even if the injection gate S is located at a not center portion, the pin member P will be inevitably curved. As a result, the through hole of the product will be eccentrical and the thickness of the wall thereof will be disunified. With reference to FIG. 8C, respecting the molding process of a basically hollow conic grip sleeve of a golf club, an upper and a lower molds are detachably joined during the molding process. After the molding process is completed, the upper and lower molds are separated for taking out the preliminary product of the grip sleeve as shown in FIG. 8C. The product has many rough edges T1-T5 at the seams L, L1, L2 formed by the joint between the molds. The portion with such seams and rough edges must be sanded and polished many times in subsequent processing. Consequently, the manufacturing cost will be greatly increased due to the labor in such processing. Moreover, the grip of the golf club is always chased with stripes and figures for the practice and appearance purposes. Such stripes and figures are often somewhat damaged during the sanding and polishing operation. Therefore, a grip with high quality can be hardly achieved.
It is known from the above that it is the only way to solve the aforesaid problems and manufacture a grip with high quality to substitute the conventional steel molds for molding the grip sleeve with a seamless steel mold. However, it is extremely difficult to make a slender seamless steel mold, not to mentioned chasing discontinuous and irregular concave and convex stripes or figures on the inner surface of a long slender tube with a length of 270 mm and an inner diameter of 14.5 mm. Even the most advanced CNC lathe at present can only operate on a plane-to-plane basis. Although the rifle line is chased in the gun barrel, the rifle line is a regular simple continuous curve. In contrast therewith, the stripes and figures of the grip sleeve of a golf club are discontinuous and irregular, so that the chasing method of the rifle line cannot be applied to the grip sleeve of a golf club.